Some people want 480p video.
Some people want 1080p video.
Some people want 4k video.
Even if the browser <video> tag did a great job at codec and resolution negotiation you still have to encode _at a minimum_ three copies of the video to hit the qualities. Multiply that each time you need a different codec for different devices.
Or, upload one video to Youtube.
Some people want 480p video.
Some people want 1080p video.
Some people want 4k video.
Even if the browser <video> tag did a great job at codec and resolution negotiation you still have to encode _at a minimum_ three copies of the video to hit the qualities. Multiply that each time you need a different codec for different devices.
Or, upload one video to Youtube.